The CMI8788 Oxygen driver -- for sound cards such as the Razer Barracuda AC-1 -- has picked up I2C support as well as support for the ASUS Xonar DX sound card. A variety of fixes and other improvements can also be found to this relatively new driver. On the topic of the intel8x0 driver with the AC97 codec, it has picked up support for eight channel audio.
The HDA codec alone has picked up more than 100 changes between ALSA 1.0.16 and 1.0.17-rc1. A few new ASICs are supported by the hda-codec such as the ALC663 and AD1883/1884A/1984A/1984B. In addition, the hda-intel driver has introduced audio support for the soon-to-be-released R700 graphics cards over HDMI (Using HDMI With ATI Linux Drivers).
Since the last ALSA release they have switched their revision control system from hg to git. The biggest disappointment with this release, however, is the continued lack of support for the Creative Sound Blaster X-Fi cards. Earlier this year 4Front Technologies had added X-Fi support to the Open Sound System thanks to some sanitized header files from Creative Labs. We had then reported that Creative was in talks with at least one ALSA developer to provide data-sheets surrounding their X-Fi APUs (Creative Joining The Open Bandwagon). However, months later we still have yet to see any sign of this Creative X-Fi support within ALSA 1.0.17.
All of the changes between ALSA 1.0.16 and 1.0.17-rc1 can be found on the ALSA Project Wiki.